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Today, more and more importance is given to the improvement of polymer materials' wear resistance, i.e., their micro-mechanical and tribological properties, which could widen their application in practice. The properties of materials can be modified by several methods, among them exposure to electron radiation. This study focuses on the effect of varying radiation intensity (15 kGy to 99 kGy), depth of penetration, and subsequent structure modification of injection-molded polypropylene on tribological and micro-mechanical properties. Electron radiation influences the structure of individual layers, thus improving or degrading their properties. Hence, the depth of penetration can be examined by instrumented hardness tests and scratch tests. Due to irradiation, surface properties and wear resistance increased by up to 105% (from 38 MPa to 78 MPa). As the results show, an increase in mechanical properties was recorded in the direction towards the center of the sample (from 72 MPa to 82 MPa). Micro-mechanical tests were also confirmed by the observation of cross-linking changes (gel test) as well as crystallinity increases (wide-angle X-ray diffraction and microtome cuts). This finding could have a significant effect on the manufacturing and subsequent modification of injection-molded polypropylene parts, which opens new possibilities in practice for this material. The increased surface wear resistance enables the use of parts for which the durability and abrasion resistance of the surface are demanded, especially in applications facing exposure to long-term cyclical loads (e.g., gears).

This publication deals with influence of tool topography (injection mould) on properties of a product. Surface of the mould was machined by various finishing technologies(milling, grinding, polishing and electrical discharge machining)which resulted in varying surface quality of the tool. The tested topography had an effect on the flow length of polymer and topographical and mechanical properties of the specimen. Examined properties(surface topography and mechanical properties)were measured in several places along the length of the product (starting at the gate and finishing at the end of the specimen). The results show that increase of the tool’s surface roughness leads to longer flow length. These findings disprove the necessity for polishing of each and every shaping part of the mould when manufacturing non-visual products. Thus, from economical and manufacturing perspective the milled or grinded tool surfaces are sufficient. Furthermore, replication of the tool’s topography is nonhomogenous, which results in varying mechanical properties throughout the product. The discrepancy in mechanical properties along the length of the product is caused by differing cooling speeds in the mould. In practice, guided cooling can be used to achieve varying mechanical properties in desired places of the injected article. For example, highly stressed parts can be manufactured with the goal of having improved mechanical properties in specific places of the product. Future application of these findings poses a significant benefit for industrial practice, as it could lower the manufacturing cost of the injection mould in order of tens of percent.

This study focuses on the problematic of polyamide 6 containing various concentrations of cross-linking agent that was exposed to electron radiation. It is important to improve the material properties of polymers as much as possible. This endeavor can be realized by numerous methods, one of which is radiation exposure. This study investigates the effect of electron beam radiation in doses ranging from 66 to 132 kGy on the micro-mechanical properties of polymers, specifically pol-yamide 6 filled with 1, 3 and 5 wt.% of cross-linking agent triallyl isocyanurate (TAIC). The changes in the material brought by the radiation exposure were quantified by measurements of indentation hardness and modulus, which were the main measured micro-mechanical properties. Furthermore, thermo-mechanical analysis (TMA) was chosen to confirm the results of the material cross-linking, while the effect of degradation was investigated by Fourier-transform infrared spectroscopy (FTIR). In pursuit of complete evaluation, the topography of the test subject’s surface was explored by atomic force microscopy (AFM). The optimal concentration/radiation ratio was found in polyamide 6 enriched by 5 wt.% concentration of TAIC, which was irradiated by 132 kGy. Material treated in such a way had its indentation hardness by 33% and indentation modulus improved by 26% in comparison with the untreated material. These results were subsequently confirmed by the TMA and FTIR methods. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

This study describes the influence of polymer flow length on mechanical properties of tested polymer, specifically polycarbonate. The flow length was examined in a spiral shaped mould. The mould cavity’s surface was machined by several methods, which led to differing roughness of the surface. The cavity was finished by milling, grinding and polishing. In order to thoroughly understand the influence of the mould surface quality on the flow length, varying processing parameters, specifically the pressure, were used. The polymer part was divided into several segments, in which the micro-mechanical properties, such as hardness and indentation modulus were measured. The results of this study provide interesting data concerning the flow length, which was up to 3% longer for rougher surfaces, but shorter in cavities with polished surface. These results are in disagreement with the commonly practiced theory, which states that better surface quality leads to greater flow length. Furthermore, evaluation of the micro-mechanical properties measured along the flow path demonstrated significant variance in researched properties, which increased by 35% (indentation hardness) and 86% by indentation modulus) in latter segments of the spiral in comparison with the gate. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Cross-linking is a process in which polymer chains are associated through chemical bonds. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behaviour. Creep value is an important parameter that describes the behaviour of a material for the duration of its exposure to long term stress. Most of the technical parts used in industry are subjected to the long term stress for their whole life cycle. This can lead to material creep, which directly results in the transformation of dimensions. To eliminate this problem, a number of construction materials was chosen and subsequently irradiated by a source of electrons. This created a 3D network within the polymer structure, which led to an increase of the micro-mechanical and micro-creep properties. Evaluation of these modifications was done by state of the art device Micro-combi tester manufactured by Anton Paar. This device lowers the time required to measure the creep by standard technology and it fluently records the changes of indentation depth in relation to applied force. This dependence is then used to calculate the creep values. Due to the electron irradiation, a 40 % increase was reached in creep resistance; therefore the useful properties of selected construction materials were improved. © Czech Technical University in Prague, 2020.

Cross-linking is a process in which polymer chains are associated through chemical bonds. The cross-linking level can be adjusted by the irradiation dosage and often by means of a cross-linking booster. The polymer additional cross-linking influences the surface nano and micro layers in the way comparable to metals during the thermal and chemical-thermal treatments. Polybutylene terephthalate (PBT) can be found in a group of structural polymers, which are often used in industry, especially in automotive. Applying the technology of electron radiation induces a creation of 3D network structure, which improves the local mechanical properties. These were later measured by a depth sensing indentation (DSI) test. This state of the art method is based on immediate detection of indentation depth in relation to applied force. The creation of 3D network caused an increase in nano-mechanical properties values, such as indentation hardness and indentation modulus, in comparison to the virgin material. The indentation hardness rose by 80%, while the indentation modulus elevated by 62%. The selected structural materials, e.g. PBT, were modified by the electron irradiation in a positive way and as such could be moved to a group of high performance materials. © Czech Technical University in Prague, 2020.

This study describes the effect of electron radiation on the nano-mechanical properties of surface layers of selected polyamide (PA) types. Electron radiation initiates the cross-linking of macromolecules in the polyamide structure, leading to the creation of a 3Dnetworkwhich fundamentally changes the properties of the tested polymers. Selected types of polyamide (PA 6, PA 66 and PA 9T) were exposed to various intensities of electron radiation (33 kGy, 66 kGy, 99 kGy, 132 kGy, 165 kGy and 198 kGy). The cross-linked polyamides' surface properties were measured by means of the modern nano-indentation technique (Depth Sensing Indentation; DSI), which operates on the principle of the immediate detection of indenter penetration depth in dependence on the applied load. The evaluation was preformed using the Oliver-Pharrmethod. The effect of electron radiation on the tested polyamides manifested itself in the creation of a 3D network, which led to an increase of surface layer properties, such as indentation hardness, elastic modulus, creep and temperature resistance, by up to 93%. The increase of temperature and mechanical properties substantially broadens the field of application of these materials in technical practice, especially when higher temperature resistance is required. The positive changes to the nano-mechanical properties as well as mechanical and temperature capabilities instigated by the cross-linking process were confirmed by the gel volume test. These measurements lay the foundation for a detailed study of this topic, as well as for a more effective means of modifying chosen properties of technical polyamide products by radiation. © 2020 by the authors.

This article deals with improving properties of surface layer of varying polymer products. Surface layer of the tested polymer was influenced by electron radiation with varying intensity. This resulted in improved resistance to wear due to creation of 3D network within the polymer structure. The properties were measured by instrumented test using a contemporary ultranano indentation device. The acquired data was then evaluated by OLIVER & PHARR method. Irradiation of surface layer caused a 16 % (26 %) improvement of mechanical properties in comparison to the unaltered material.

Injection moulding is a manufacturing process which is suitable for high-volume production of polymer parts. These products are final and do not require any additional operations. The quality of the final product is significantly affected by the surface of the mould cavity. This paper reveals the influence of cavity surface roughness and technological parameters on the flow length of polyoxymethylene (POM) into the mould cavity. These results indicate that costly finishing methods used for working of mould cavities can be replaced with less expensive manufacturing methods. Furthermore, it might be possible to shorten the time necessary for the production of the injection mould. © 2020, MM publishing Ltd. All rights reserved.

The goal of this study was to determine the extent, to which beta radiation modified mechanical properties of surface layer on scale of nano meters. The current trend of replacing varying metal products by plastic products leads to lesser weight, but also a decrease of the tear resistance. This can be countered by exposing the material to electron radiation, which causes a creation of 3D network within the polymer structure. This process is an equivalent to heat treatments of metals. Properties of irradiated polyamide (hardness, modulus, deformation work, creep, etc.) were tested by contemporary indentation method (NHT3). This data was then evaluated by OLIVER & PHARR method. The results have shown that modifying the surface layer of polyamide led to a 50 % increase of mechanical properties. © 2020, MM publishing Ltd.. All rights reserved.

This article deals with the influence of the radiation cross-linking of polyamide 11 (PA 11) on the mechanical properties. The aim of this study is to provide more detailed knowledge of the relation between the radiation dosage and the properties of cross-linked PA 11 and its mechanical behaviour. Electron-beam-unmodified and modified PA 11 test samples were exposed to electron radiation with dosages from 0 kGy to 198 kGy, which were graded at 33 kGy. The surface-layer properties of the modified PA 11 were tested using a state-of-the-art indentation technique, which detects the immediate change in the indentation depth, depending on the applied force. The evaluation of the measured mechanical properties (indentation hardness, modulus and creep) was done by the Oliver and Pharr method. A significant influence of the radiation cross-linking on the PA 11's mechanical properties improvement was confirmed by the measurements. This enhancement grows with the increasing radiation dosage. Due to the electron-radiation modification of PA 11, the mechanical properties of the surface layer were increased by up to 59 % compared with the unaltered material. Radiation crosslinking is an important thermoplastic modification method by which the desired properties can be achieved in a relatively short period of time. The main advantage is that the process is executed on the final product.

This study's goal was to describe the influence of a wide range of ionizing beta radiation upon the changes in surface layer mechanical properties and structural modifications of selected types of polymer. Radiation crosslinking is a process whereby the impingement of high-energy electrons adjusts test sample structures, thus enhancing the useful properties of the material, e.g., hardness, wear-resistance, and creep, in order that they may function properly during their technical use. The selected polymers tested were polyolefin polymers like polyethylene (Low-density polyethylene LDPE, High-density polyethylene HDPE). These samples underwent exposure to electron radiation of differing dosages (33, 66, 99, 132, 165, and 198 kGy). After the crosslinking process, the samples underwent testing of the nano-mechanical properties of their surface layers. This was done by means of a state-of-the-art indentation technique, i.e., depth-sensing indentation (DSI), which detects the immediate change in the indentation depth associated with the applied force. Indeed, the results indicated that the optimal radiation dosage increased the mechanical properties by up to 57%; however, the beneficial levels of radiation varied with each material. Furthermore, these modifications faced examination from the structural perspective. For this purpose, a gel test, Raman spectroscopy, and crystalline portion determination by X-ray all confirmed the assumed trends. © 2020 by the authors.

In recent years, materials with natural fillers have begun to be used for manufacturing window frames and various linings. These compounds can replace natural materials such as wood and stone. The main reasons to use these fillers are price (which is lower than that of a polymer) and rigidity. The resulting product is strong, hard, light, possesses a long-term resistance to wind abrasion and takes on the appearance of wood and stone. The type of filler has a significant effect on the final properties of the material. In the past, however, insufficient attention was paid to the effect of natural fillers on the injection-molded product's mechanical properties. First, the test samples were measured by depth sensing indentation (DSI), which is a contemporary instrumented hardness test used to determine the micro-mechanical properties. A Micro Combi Tester made by the Anton Paar company was used for these tests. Then, the measurements were evaluated by the Oliver and Pharr method. The goal of this study was to prepare a low-density polyethylene (LDPE) filled with varying natural fillers, e.g., finely ground wood, coarsely ground wood and slate) and its subsequent granulation. The implementation of these fillers led to an increase of the mechanical properties, e.g., indentation hardness and modulus, by up to 100 % in comparison with the virgin material. The goal of this study was to evaluate the effect of natural fillers, such as wood and slate, on the mechanical properties of the tested materials.

Good quality of surface layer is an important aspect for correct function and longevity of final product. Surface layer was modified by beta radiation with differing intensity. Radiation caused creation of three dimensional spatial network, which directly leads to improvements of the tested polymer’s (PA11, PA12) surface properties. Surface properties (micro-creep) were measured by micro-indentation test on MHT3 machine. Goal of this paper is to modify the surface layer (by using several different intensities of beta radiation) in a way, that causes increase in resistance against long term stress (micro-creep) in the final product, which is an important property that ensures correct function of the product. The changes in micro-creep were compared and afterwards confirmed by the use of gel test, which showed what percentage of the whole part was cross-linked. © 2019 Trans Tech Publications Ltd, Switzerland.

Modification of polymers by fillers is one of the most used material alterations to improve its required properties. This article is about modification of polymer matrix by fillers with layered particles. Linear low density polyethylene (LLDPE) was used as matrix and it was mixed with different kinds of fillers. Fillers used were: CaPhP – Calcium Phenylphosphonate, double layered hydroxides (ZnAl-DDS, ZnAl-lac and ZnAl-CO3) and natural Talc. Individual fillers were mixed into the matrix by kneading machine with the use of several velocities. The article focuses on influence of the individual filler on mechanical properties measured by tensile strength test. This paper also investigates the problem of process parameters’ influence on final mechanical properties and later confirms positive impact of all fillers that were used, although the size of them differs. © 2019 Trans Tech Publications Ltd, Switzerland.

Surface properties are important aspect for correct function of construction (technical) parts. By improving mechanical properties of surface, an increase of abrasion resistance and wear resistance is reached. Longevity and economical aspect have an important role in final useful properties of product. Measurement of surface properties was done by ultra-nano indentation technique (UNHT3), this is the best tool available right now, this technique is based on instrumented testing. Surface properties were modified by ionized radiation, that caused the creation of crosslinked structure in polyethylene. During radiation a three dimensional network is created, that improves final properties of product such as: hardness, elasticity modulus, thermal stability, etc. During ionized radiation there are two actions that take place at the same time, crosslinking and degradation. Goal of this paper is to consider how radiation intensity affects surface properties (indentation hardness, indentation modulus, deformation work, etc.) Another goal of this paper is to find out the optimal dose of radiation, that will cause more three dimensional crosslinking and less degradation as degradation causes decrease in mechanical properties. © 2019 Trans Tech Publications Ltd, Switzerland.

This article deals with the issue of the amount of clay type nano-fillers used for the improvement of mechanical properties of the basic material HDPE. These fillers already showed their positive influence on various mechanical properties. This article is primarily concentrated on the percentage of filling, which has the significant influence on these properties and also on the final product price in which is the price of used fillers included. It is desirable to find a suitable concentration of filling of the basic material for the improvement of creep properties. As a percentage of filling the lower concentrations were used which are in the practice more common in connection with the nanofillers which have a high ratio of shape dimensions. © 2019, MM publishing Ltd. All rights reserved.

This article deals with the use of Ultra-nano indentation Tester UNHT 3 for the measurement of (ultra nano) mechanical properties. The effect of electron beam (EB) radiation on Polybutylene terephthalate (PBT) was investigated. To clarify whether crosslinking could take place without or only with the presence of a crosslinking agent, special attention was paid to the incorporation of this agent into tested polymer. In this study we have investigated the effect of crosslinking agent, and instantaneously electron beam radiation-induced crosslinking in the presence of Triallyl cyanurate on various mechanical properties of PBT. The results show that the influence of radiation has improved the observed properties in the surface layer. The increase in ultra-nano properties was around 26% over the basic material. Engineering plastics like Poly (butylene terephthalate) due to their desirable properties have various industrial applications. © 2018, North Atlantic University Union. All rights reserved.

This article deals with the influence of electron beam radiation on nano-mechanical properties and the structure of polyamide 11. Crosslinking of polymers is a process, during which macromolecular chains start to connect to each other and the spatial network creates in the structure. During the action of the ionizing radiation two actions can occur: crosslinking and scission of macromolecules – degradation. Both these processes run parallel. Using the crosslinking technology the standard and construction polymer can obtain the more “expensive” high-tech polymeric materials properties and thus replace these materials in many applications. Tested material was irradiated by different doses of beta radiation (33, 66 and 99 kGy). The nano-mechanical properties were measured using DSI method, which fluently records the change of the indentation in time. From this dependence it is possible to determine nano-mechanical properties such as indentation hardness, indentation modulus etc. During results consideration it is obvious that irradiation acts on each polymer differently, but always when the optimal dose was found, nano-mechanical properties increased up to 34 %. The changes of nano-mechanical properties were confirmed by structural measurement when the change of hardness and modulus corresponded to gel content. © 2018, North Atlantic University Union. All rights reserved.

This article deals with the influence of electron beam radiation on nano-mechanical properties and the structure of polyamide 11. Crosslinking of polymers is a process, during which macromolecular chains start to connect to each other and the spatial network creates in the structure. During the action of the ionizing radiation two actions can occur: crosslinking and scission of macromolecules-degradation. Both these processes run parallel. Using the crosslinking technology the standard and construction polymer can obtain the more "expensive" high-tech polymeric materials properties and thus replace these materials in many applications. Tested material was irradiated by different doses of beta radiation (33, 66 and 99 kGy). The nano-mechanical properties were measured using DSI method, which fluently records the change of the indentation in time. From this dependence it is possible to determine nano-mechanical properties such as indentation hardness, indentation modulus etc. During results consideration it is obvious that irradiation acts on each polymer differently, but always when the optimal dose was found, nano-mechanical properties increased up to 34 %. The changes of nano-mechanical properties were confirmed by structural measurement when the change of hardness and modulus corresponded to gel content. © 2018 The Authors, published by EDP Sciences.

This article deals with the use of Ultra-nano indentation Tester UNHT3 for the measurement of (ultra nano) mechanical properties. The effect of electron beam (EB) radiation on Polybutylene terephthalate (PBT) was investigated. To clarify whether crosslinking could take place without or only with the presence of a crosslinking agent, special attention was paid to the incorporation of this agent into tested polymer. In this study we have investigated the effect of crosslinking agent, and instantaneously electron beam radiation-induced crosslinking in the presence of Triallyl cyanurate on various mechanical properties of PBT. The results show that the influence of radiation has improved the observed properties in the surface layer. The increase in ultra-nano properties was around 26% over the basic material. Engineering plastics like Poly (butylene terephthalate) due to their desirable properties have various industrial applications. © 2018 The Authors, published by EDP Sciences.